This invention relates to a method of applying a treatment liquid to a semiconductor wafer to form a coating and to an apparatus for carrying out the method.
In the manufacture of semiconductor devices, various liquid chemicals, which will hereinunder be collectively referred to as treatment liquids, must be applied to the surface of a semiconductor wafer to form coating. One commonly-used method of applying these treatment liquids is referred to as spin coating. In this method, a semiconductor wafer is supported atop a chuck which is rotated at a high speed. A treatment liquid is dripped or sprayed onto the center of the top surface of the wafer, and the centrifugal force which acts on the treatment liquid causes it to spread outwards over the surface of the wafer and form a uniform coating.
FIG. 1 schematically illustrates a conventional spin coating apparatus. A wafer chuck 1 which rotates at a high speed is disposed inside a hermetically-sealed container 2. A semiconductor wafer 3 is held to the top surface of the chuck 1 by suction. As the wafer 3 is rotated by the chuck 1, a treatment liquid 5 is sprayed onto the top surface of the wafer 3 through a nozzle 4. A portion of the treatment liquid 5 is scattered by centrifugal force beyond the wafer 3. Upon striking the inner surface 2a of the sealed container 2, the treatment liquid 5 flows downwards and is removed from the sealed container 2 via exhaust pipes 6.
When a large number of wafers 3 are coated with a treatment liquid using an apparatus of this type, the inner surface 2a of the sealed container 2 becomes covered with drops of the treatment liquid 5, and a substantial amount of mist of the treatment liquid 5 is formed. A portion of the mist adheres to the top surface 3a of the wafer 3, producing defects in the pattern on the wafer 3 and decreasing the yield of wafers 3.